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| United States Patent |
5,271,951
|
|
Ando
|
December 21, 1993
|
Powdery oyster juice composition, process for the production of the
same, and process for retaining the freshness of perishable food with
the use of powdery oyster juice composition
Abstract
A powdery oyster juice composition comprises oyster juice and lactose. A
process for the production of the powdery oyster juice composition
comprises mixing an oyster juice concentrate with lactose and drying the
mixture in such a manner as to reduce the moisture content of the mixture
to 5% or below. A process for retaining the freshness of a perishable
food, for example fish, shellfish, livestock meats and vegetables,
comprises contacting the food with the powdery oyster juice composition or
an aqueous solution thereof. The powdery oyster juice composition, which
is excellent in preservability and handleability, makes it possible to
retain the freshness of a refrigerated or cold-stored perishable food on a
level comparable to that before refrigeration or cold storage.
| Inventors:
|
Ando; Yoshimi (3-18, Gokiso-Dori, Showa-ku, Nagoya-shi, Aichi-ken, JP)
|
| Appl. No.:
|
665516 |
| Filed:
|
March 5, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
426/655; 426/471; 426/589; 426/590 |
| Intern'l Class: |
A23C 021/08; A23L 001/327; A23L 002/08; A23L 003/00 |
| Field of Search: |
426/471,655,590,589
|
References Cited
U.S. Patent Documents
| 1876090 | Sep., 1932 | Strasburger | 426/589.
|
| 3262788 | Jul., 1966 | Swanson et al. | 426/593.
|
| 3634103 | Jan., 1972 | Lowe et al. | 426/471.
|
| 3634128 | Jan., 1972 | Bolin | 426/330.
|
| Foreign Patent Documents |
| 2007489 | May., 1979 | GB | 426/589.
|
Primary Examiner: Hunter; Jeanette
Assistant Examiner: Mims; Mary S.
Attorney, Agent or Firm: Lowe, Price, LeBlanc & Becker
Claims
I claim:
1. A process for retaining the freshness of a perishable food, comprising
contacting a perishable food with an oyster juice composition comprising
oyster juice and lactose wherein the oyster juice composition contains a
weight ratio of oyster juice to lactose of at least 0.05:1.
2. A process as defined by claim 1, wherein the oyster juice composition is
in powder form.
3. A process as defined by claim 1, wherein the oyster juice composition
includes water.
4. A process as defined by claim 1, wherein the perishable food is
contacted with the oyster juice composition prior to refrigeration of the
perishable food.
5. A process as defined by claim 1, wherein the perishable food is
contacted with the oyster juice composition subsequent to refrigeration of
the perishable food.
6. A process as defined by claim 1, wherein the perishable food is
contacted with the oyster juice composition prior to cold storage of the
perishable food.
7. A process as defined by claim 1, wherein the perishable food is
contacted with the oyster juice composition subsequent to cold storage of
the perishable food.
8. A process as defined by claim 1, wherein the oyster juice composition is
prepared by steaming oysters in the shell, drying the same and collecting
drippings therefrom to obtain oyster juice, mixing the oyster juice with
lactose, and drying the resulting mixture to reduce the moisture content
of the mixture to 5% or less.
9. A process as defined by claim 8, wherein the drippings are filtered and
concentrated to at least 28.degree. Be.
10. A process as defined by claim 8, wherein the oyster juice composition
is in powder form.
11. A process as defined by claim 8, wherein the oyster juice composition
further includes water.
12. A process as defined by claim 8, wherein the lactose comprises lactose
monohydrate.
13. A process as defined by claim 12, wherein the weight ratio of oyster
juice to lactose monohydrate is 0.05:1 to 0.1:1.
14. A process as defined by claim 1, wherein the lactose comprises lactose
anhydride.
15. A process as defined by claim 14, wherein the weight ratio of oyster
juice to lactose anhydride is 0.05:1 to 0.15:1.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a powdery oyster juice composition, a process for
the production of the same, and a process for retaining the freshness of
perishable foods for example fish, shellfish, livestock meats and
vegetables, with the use of said powdery oyster juice composition.
2. Description of the Prior Art
A common means for retaining the freshness of perishable foods comprises
refrigeration or cold storage thereof. In particular, refrigeration is an
indispensable means for the prolonged storage of fishes, shellfishes and
livestock meats. However there has been provided no effective means for
avoiding or preventing the deterioration (for example, drying or
oxidation) thereof during storage in a frozen state, though rapid chilling
and glazing are effective therefor to some extent. Further, it is
unavoidable in thawing frozen foods that the textures of fishes,
shellfishes or livestock meats suffer from some changes. Namely, it is
very difficult to restore these thawed foods to a state before
refrigeration. When vegetables are frozen, the freezing of the moisture
contained in their cells causes destruction of their textures, so that
most of the frozen vegetables cannot be restored to a state before
refrigeration. Therefore vegetables are usually cold-stored. In this case,
however, they suffer from some troubles including drying during cold
storage thereof.
When perishable foods such as fishes or shellfishes (including prawns and
crabs) which have not been heat-treated are rapidly chilled and then
thawed, the textures of the foods are weakened as compared with those
before chilling, even when they are neither dried nor oxidized. In the
case of shucked prawns, for example, an unfrozen fresh prawn is bent just
like a hook when hung bottom up. In contrast, a shucked prawn, when frozen
and thawed, forms into a stick when hung in the same manner. When picked
with fingers, the trunk of an unfrozen fresh prawn is tight and elastic,
while the trunk of a frozen and thawed prawn is soft and less elastic.
This difference in elasticity between the unfrozen and frozen prawns is
clearly noticeable when they are taken uncooked, for example, as sashimi.
When roasted directly on fire or on an iron plate, an unfrozen prawn
undergoes little shrinkage and is juicy, while a frozen and thawed prawn
undergoes serious shrinkage and is not juicy. The above-mentioned
differences in elasticity, shrinkage upon roasting and juiciness between
the unfrozen and frozen prawns are similarly observed in other fishes and
such as the adductor muscle of a scallop, and in livestock meats.
SUMMARY OF THE INVENTION
The present invention has conducted extensive studies on a process for
retaining the freshness of perishable foods and unexpectedly has found out
that oyster juice is effective in retaining the freshness of perishable
foods. Further, he has succeeded in the application of a powdery oyster
juice composition, according to the present invention, to the retention of
the freshness of perishable foods. Accordingly, the present inventor has
succeeded in retaining perishable foods, either frozen and then thawed or
cold-stored and then brought to room temperature, in a state substantially
the same as that before refrigeration or cold storage, by contacting the
foods with a powdery oyster juice composition comprising oyster juice and
lactose or an aqueous solution thereof before or/and after refrigeration
or cold storage.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
An oyster juice is a drip formed when an oyster in the shell is steamed,
and is a by-product obtained in the preparation of dry oysters for Chinese
dishes by drying heated oysters. It can be obtained by extracting heated
oysters with water and then concentrating the extract. Different from an
oyster extract having an intense body, this drip (i.e., oyster juice) has
little body and thus has been discarded in most cases.
However the drip (oyster juice) is poor in preservability or handleability
as such, and the result of subsequent studies conducted to solve this
problem has proved that a powdery oyster juice composition which is
excellent in preservability, can be easily handled and which has an effect
of retaining the freshness of perishable foods can be obtained by
concentrating the drip to thereby give an oyster juice concentrate in the
form of a syrup, mixing the concentrate with lactose, and drying.
The powdery oyster juice composition may be prepared in the following
manner.
(1) Preparation of Oyster Juice Concentrate
Dry oysters are prepared by steaming oysters in the shell, followed by
drying. The drip obtained in this step is filtered, if required, and
concentrated to at least 28.degree. Be to thereby give an oyster juice
concentrate. (This concentrate is in the form of a pale brown syrup and
contains common salt, glycogen, nitrogen compounds, etc. However it does
not have a body so intense as that of so-called oyster extract prepared by
heating and extracting oyster meat with water and concentrating the
extract.)
(2) Mixing of Oyster Juice Concentrate with Lactose
Lactose is used as a binder for powdering the oyster juice. The lactose may
be a commercially available one and either monohydrate or anhydride may be
employed. The oyster juice concentrate and lactose are mixed with, for
example, a kneader so as to give a moist mixture (powder). Regarding the
mixing ratio, it is appropriate to use 0.05 to 0.1 part (by weight, the
same will apply hereinafter) of the oyster juice concentrate per part of
lactose monohydrate or to use 0.05 to 0.15 part of the oyster juice
concentrate per part of lactose anhydride. When the ratio of the oyster
juice concentrate to the lactose is smaller than 0.05, the effect of the
resulting powdery oyster juice composition of retaining the freshness of
perishable foods is deteriorated. When it exceeds 0.1 (in the case of
lactose monohydrate) or 0.15 (in the case of lactose anhydride), on the
other hand, the resulting mixture of the oyster juice concentrate with
lactose becomes sticky, which causes some troubles in the preparation
procedure such that the subsequent drying step becomes difficult or that
the dried material forms a large and hard mass. A mixture having the
mixing ratio as specified above is in the form of a somewhat moist and
crispy material which can be easily handled and efficiently dried in the
subsequent drying step.
(3) Drying
It is preferable to continue the drying until the moisture content of the
mixture is lowered to 5% or below. The drying may be performed by a
conventional method such as hot-air drying or lyophilization. It is
sometimes observed that a portion of the dried mixture forms a soft mass,
which is ground, if required.
In the above process, the mixing (2) and the drying (3) are separately
performed. Alternately, the mixing and the drying may be continuously
carried out in a single step by feeding the oyster juice concentrate to a
fluidized lactose layer formed by hot air at the mixing ratio as specified
above.
The powdery oyster juice composition thus obtained may be further mixed
with an additional oyster juice concentrate and dried. By repeating this
procedure once or several times, a composition having a high
freshness-retaining effect per unit weight may be obtained.
The powdery oyster juice composition thus prepared has an excellent
preservability, can be easily handled in use since it is in the form of a
powder, and is readily soluble in water.
According to the present invention, the freshness of perishable foods may
be retained by contacting the foods, either before or after refrigeration
or cold storage, with a powdery oyster juice composition or an aqueous
solution thereof. The contact may be effected by, for example, immersing
the food in an aqueous solution of the powdery oyster juice composition
for a given period of time, spraying an aqueous solution of the powdery
oyster juice composition to the food, or dusting the powdery oyster juice
composition onto the food. It is also effective to contact the perishable
food with the powdery oyster juice composition or an aqueous solution
thereof both before and after refrigeration or cold storage.
When the powdery oyster juice composition is to be used in the form of an
aqueous solution, the concentration thereof may be preferably 1% or above,
still preferably 3% or above. It is also possible to use a suspension of
the powdery oyster juice composition in water. The aqueous solution of the
powdery oyster juice composition may further contain other components such
as common salt, if required. When a perishable food is to be immersed in
the aqueous solution of the powdery oyster juice composition, the
immersion time may range from approximately 5 to 30 minutes, though it may
vary depending on the type and size of the food. The immersion temperature
may be appropriately selected. It is further effective to thaw a frozen
perishable food while immersing it in the above-mentioned aqueous
solution.
Perishable foods (for example, fish, shellfish, or livestock meats) treated
according to the present invention scarcely cause dripping and are
substantially free from fishery smell. They have tight and elastic
textures comparable to unfrozen ones. When cooked by heating, they undergo
little shrinkage like the unfrozen ones and are juicy. These facts are
highly effective not only in improving the taste and palatability but also
in increasing the yield of the product.
To further illustrate a process for the production of the powdery oyster
juice composition of the present invention and a process for retaining the
freshness of perishable foods with the use of said powdery oyster juice
composition, the following examples will be given.
EXAMPLE 1
10 kg of lactose monohydrate was fed into a kneader and 1 kg of an oyster
juice concentrate of 28.degree. Be was added thereto under stirring. When
a homogenous mixture was obtained, the mixture was taken out of the
kneader and spread on a drying pan. Then it was dried with a hot-air dryer
at 75.degree. C. for 50 minutes. The whole material thus dried was then
fed into the kneader again and 1 kg of the oyster juice concentrate of
28.degree. Be was further added thereto under stirring. The
above-mentioned hot-air drying was repeated and the whole material thus
dried was fed into the kneader once again. Next, 0.8 kg of the oyster
juice concentrate of 28.degree. Be was added thereto under stirring. After
repeating the above-mentioned hot-air drying at 75.degree. C. for 1 hour
and 10 minutes, 8.7 kg a powdery oyster juice composition containing 2% of
moisture and 0.5% of nitrogen was obtained.
EXAMPLE 2
15 head-less prawns occurring in China were immersed in an aqueous solution
of 10 g of the powdery oyster juice composition produced in Example 1 and
15 of common salt in 500 ml of water at 23.degree. C. for 20 minutes.
After draining, the prawns were rapidly chilled at -37.degree. C. The
chilled prawns were stored in a freezer for 37 days and then thawed at
0.degree. C. (sample of test lot).
As a control, 15 head-less prawns occurring in China were rapidly chilled
at -37.degree. C. immediately. After storing in a freezer for 37 days, the
prawns were thawed at 0.degree. C. (samples of control lot).
The following Table shows the comparison of the samples of the test lot
with those of the control lot.
______________________________________
Test lot
Control lot
______________________________________
Yield (%)* 99 96
Elasticity after thawing
yes little
______________________________________
Note:
*Yield (%) = (weight after thawing/weight thawing) .times. 100
Further, the samples of the test and control lots were prepared into
sashimi and taken by 10 panelists so as to conduct a triangle difference
test (organoleptic evaluation; cf. note 1).
______________________________________
No. of panelists
No. of panelists
No. of panelists
giving correct
preferring test
preferring control
answer sample sample
______________________________________
10 10 (cf. note 2)
0
______________________________________
Note
1: This test comprises arbitrarily combining one or two samples of the
test lot (A) with two or one sample of the control lot (B) to thereby giv
combinations of three samples, for example, (AA-A, AB-B), giving the
samples to the panelists, and counting the panelists who correctly
selected two samples from the same lot and one from another lot. Among
these panelists giving the correct answers, those preferring samples of
each lot were counted.
2: Reason for the preference: (1) the sample has taste and palatability
similar to those of fresh prawns; (2) the sample gives no fishery smell.
The above test has proved that the prawns treated in accordance with the
present invention are much superior to the untreated ones in, for example,
yield and preference.
EXAMPLE 3
The adductor muscles of living scallops were immersed in an aqueous
solution of 10 g of the powdery oyster juice composition produced in
Example 1 and 10 g of common salt in 500 ml of water at 27.degree. C. for
20 minutes. After draining, they were rapidly chilled at -37.degree. C.
After storing in a freezer for 48 days, the muscles were taken out and
thawed (samples of test lot).
As a control, the adductor muscles of scallops were similarly taken out and
rapidly chilled at -37.degree. C. immediately. After storing in a freezer
for 48 days, they were taken out and thawed (samples of control lot).
The following Table shows the comparison of the samples of the test lot
with those of the control lot.
______________________________________
Test lot Control lot
______________________________________
Yield (%)* 100 99
Elasticity after
comparable to soft and less
thawing fresh one elastic
Fishery smell little serious
Shrinkage upon
90 70
roasting on iron
plate (%)**
______________________________________
*Yield (%) = (weight after thawing/weight before thawing) .times. 100
**Shrinkage (%) = (diameter of roasted muscle/diameter of unroasted
muscle) .times. 100 (average of 10 samples). A Tefloncoated iron plate wa
used at a surface temperature of 180.degree. C.
Furthermore, samples of the test lot and those of the control lots were
roasted on the iron plate and taken by 10 panelists so as to conduct a
triangle difference test (organoleptic evaluation).
______________________________________
No. of panelists
No. of panelists
No. of panelists
giving correct
preferring test
preferring control
answer sample sample
______________________________________
10 10 (cf. note 2)
0
______________________________________
Note
2: Reason for the preference: (1) the sample has taste and palatability
similar to those of roasted fresh scallop adductor muscles; (2) the sampl
is juicy.
The above test has proved that the scallop adductor muscles treated in
accordance with the present invention are much superior to the untreated
ones in, for example, yield and preference.
EXAMPLE 4
20 eels split alive were divided into two groups each consisting of 10
fish. The eels of one group were rapidly chilled at -37.degree. C.
immediately (control lot). On the other hand, the eels of another group
were immersed in an aqueous solution of 20 g of the powdery oyster juice
composition produced in Example 1 and 60 g of common salt in 2000 ml of
water at 26.degree. C. for 30 minutes and then rapidly chilled at
-37.degree. C. (test lot). After storing in a freezer for 1 week, the eels
were taken out and thawed in another freezer at 0.degree. C. The thawed
eels were steamed for 5 minutes and then roasted in an electric heater
while applying a marketed tare (seasoning sauce) to thereby prepare
kabayaki. The following table shows the yield in each step and the
organoleptic evaluation.
______________________________________
Yield in control lot
Yield in test lot
______________________________________
Freezing/thawing
96.4% 97.1%
Thawing/steaming
88.5% 91.9%
Steaming/roasting,
71.6% 75.1%
seasoning
______________________________________
Further, these kabayaki products were taken by 10 housewives. As a result,
all of them answered that those of the test lot were easy to take, since
they were swollen, voluminous and freed from persistent smell.
EXAMPLE 5
5 raw horse mackerels were sliced in three layers and one of the fillets of
each fish was immersed in an aqueous solution of 20 g of the powdery
oyster juice composition produced in Example 1 and 70 g of common salt in
1000 ml of water at 24.degree. C. for 1 hour and 30 minutes. After
draining, these fillets were rapidly chilled at -37.degree. C. After
storing in a freezer for 1 day, they were taken out and spontaneously
thawed (samples of test lot).
As a control, another fillet of each fish was immersed in an aqueous
solution of 70 g of common salt in 1000 ml of water at 24.degree. C. for 1
hour and 30 minutes. After draining, these fillets were rapidly chilled at
-37.degree. C. After storing in a freezer for 1 day, they were taken out
and spontaneously thawed (samples of control lot).
The samples of the test and control lots were evaluated as follows.
Evaluation in Untreated State
The samples of the control lot were glossy but not transparent, whereas
those of the test lot were glossy and transparent, thus giving a
freshness.
Compared with the samples of the control lot, those of the test lot were
voluminous and had high elasticity.
Although both of the samples of the test and control lots had a fishery
smell, no offensive odor was noticeable.
Evaluation in Roasted State
During the roasting procedure, the samples of the test lot looked oily
compared with those of the control lot. The former could be roasted within
a shorter period and the whole fillets showed a well roasted color.
The samples of the test lot had a nice roasted smell without any offensive
odor as compared with those of the control lot. Further, the former had a
sweet taste and gave an impact when taken mouthful.
EXAMPLE 6
Lettuce leaves were divided into 3 groups. The first group was allowed to
stand at room temperature (control lot); the second group was allowed to
stand at room temperature after water spraying (water-treated lot); and
the third group was allowed to stand at room temperature after being
sprayed with an aqueous solution of 2 g of the powdery oyster juice
composition produced in Example 1 in 100 ml of water (test lot). The
following table shows changes in the weight and appearance of these
lettuce leaves after one and two days.
______________________________________
Control
Water-treated
Test
lot lot lot
______________________________________
Leaf weight (g)
1 day 224 174 169
after 2 days 207 260 256
Tension after
1 day no yes yes
2 days no no yes
Gloss after
1 day no no yes
2 days no no yes
______________________________________
According to the present invention, as described above, a powdery oyster
juice composition which is effective in retaining the freshness of
perishable foods can be obtained. In addition, said powdery oyster juice
composition is excellent in preservability and can be easily handled.
When a frozen perishable food which has been treated with said powdery
oyster juice composition is thawed, the food shows a freshness nearly
comparable to that before freezing. When a cold-stored perishable food
which has been treated with said powdery oyster juice composition is
brought to room temperature, the food showed a freshness nearly comparable
to that before cold storage.
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